How To Get 'Dirt' from Clean Channel?

[exocet]

This may be a very stupid question as I am not experienced with D Style amps.

I have a 50 Watt Non HRM High Plate derivation of #124.

Should the clean channel be capable of delivering a bit of 'dirt' to add interest to chords / double stops or is it always going to be pristine clean even with channel gain set at max?

The reason I ask is that I discovered this clip on You Tube

http://www.youtube.com/watch?v=2KV9ZO7CJvY

It features a Brown Note Bluesmaster (Blue Monkey?). I am trying to work out whether everything is played with OD engaged or whether even the clean channel is giving a nice 'dirty sound'. It's the opening chords that I like, very SRV.

To summarise - how do I get a similar sound? Does it require Bluesmaster configuration? Does Bluesmaster give nice breakup when gains are pushed high on clean channel?

Many thanks

Exocet

[Bob-I]

I hope Normster or Moss jump in here, but to my ears that sounds like OD throughout the entire clip. It's set fairly low so it cleans up nicely with just a light touch.

To me this is the best part of the Dumble style OD, it changes timbre so easily with touch.

[dogears]

Use 150K/120K plates on clean. 4.7uf bypass. 2.2K/1.8K cathode resistors. Bluesmaster tonestack. Megaboost implementation. Clean channel gets some serious singing gain and feedback!

[exocet]

Thanks Scott.

As usual that raises another question, what is 'megaboost'? The only technical reference I've found on the forum refers to lifting the "mid leg from ground".

Can you shed any more light?

Thanks

[Bob Simpson]

Use 150K/120K plates on clean. 4.7uf bypass. 2.2K/1.8K cathode resistors. Bluesmaster tonestack. Megaboost implementation. Clean channel gets some serious singing gain and feedback!

I was just going to ask that...

Bob

[ayan]

Thanks Scott.

As usual that raises another question, what is 'megaboost'? The only technical reference I've found on the forum refers to lifting the "mid leg from ground".

Can you shed any more light?

Thanks

That is really it, you just lift the ground connection from the middle pot -- and remember the BM has what looks like a Fender tone stack. That way you get rid of that huge signal loss which occurs at the tone stack and you have more gain available from the clean channel.

Gil

[Tonegeek]

+1 on dogears reply. If you end up with too much bass (mega boost off), which could happen if you run a box with more than one speaker, try increasing the slope resistor value (stock BM one is 47k). There are other ways to balance the tone too, but this worked best for me.

[tubedogsmith]

I've built a couple 50 watt amps and the clean channel seems to have plenty of breakup with both high and low plate resistors. I'm suprised you'd have a 50 watter that wouldn't give it up in the clean channel. I guess it could just be defintion.

[Structo]

Yes, I have no problem dialing in breakup on the clean channel.

If you turn up the pre gain volume and keep the master down, it should break up pretty easily.

In fact, I can make it so the difference between the clean and overdrive channel isn't very big at all tone wise.

You just need to twist some knobs.

What power tubes are you using?

[Tonegeek]

I've built a couple 50 watt amps and the clean channel seems to have plenty of breakup with both high and low plate resistors. I'm suprised you'd have a 50 watter that wouldn't give it up in the clean channel. I guess it could just be defintion.

We might be talking apples and oranges here. I assumed the poster was talking just about getting the channel to break up against the master volume, regardless of how loud the master was turned up. You seem to be implying that the power section is part of the equation. I could force my 50 watt skyliner to break up the power section if I turned it up loud enough, but the channel itself was very clean even cranked wide open. The BM configuration seems to break up the channel a bit earlier and has more harmonic content all the way around than the Skyline, especially the high plate Skyline. Just my observation having tried many combinations of plate and tone stack values.

[exocet]

When I crank up the Volume (master set low), the only 'distortion' that I can perceive is tube compression...which in itself is quite nice but it still sounds pretty clean. I always assumed that the D sound was mainly shaped in the preamp rather than rely upon Power Tube saturation ala Marshall.

If I engage PAB then it does 'break up' but the overall tonality is not that pleasing.....it lacks 'bite' and 'definition'.

My only other valve amp is a 1960's Marshall JTM50 that I equipped with a PPIMV, no problem getting distortion there with the master turned down...problem is Marshall Preamp distortion is not that good!! I was expecting to be able to do the same with the D clone.

I think that Gill has 'hit the nail on the head' with reference to the Fender tonestack which from my limited knowledge is much more lossy compared to Marshall therefore no PI valve overload when you crank up the channel gain?

My guitar is a telecaster no no High Output humbuckers.

In general, do D style amp users playing Blues / Rock rely upon having the OD engaged and then clean the sound up with guitar volume....perhaps kicking in the PAB for more aggressive sounds?

I think I'll try Dogears suggestions and see where I end up. Is there a consensus on BLuesmaster tonestack values? I've searched on the forum and am not that clear as to what Bluesmaster really entails.

Thanks for you help, it really is appreciated.

[talbany]

The BM configuration seems to break up the channel a bit earlier and has more harmonic content all the way around than the Skyline, especially the high plate Skyline. Just my observation having tried many combinations of plate and tone stack values.

I would think most of the harmonic content you are hearing is due to the different Phase inverters 9K tail and 470 ohn cathode not as much headroom there... Having a larger tail resistance (like 124# 22k) limits the maximum output voltage swing, which is of particular concern for high-power amps. For this reason a smaller tail is often required, which causes the inverted phase to have substantially more amplification(see below) than the non-inverted phase. The usual correction is to reduce the size of the inverting plate resistor. The 9K tail causes a bit more of an in balance when it hits the rails...Asymetrical clipping.... To my ears I hear thicker tone but more grit associated with a clipping PI none the less more distortion.. The BM PI uses less NFB around the power amp, which also opens the amp ." any one of these by them selves not a big difference put them together more harmonic content... Not disagreeing with you just coming from a different angle..

Gain here is not much of a factor..Just the inbalance!!

Fender Style 12ax7 100k pl 22kt 820 =Inverted output -26.9155
In Phase output 25.465

Blues Master/ Marshall 12ax7 100k pl 10Kt 470=inverted output -27.720
In phase 24.660


Tony VVT

[greiswig]

The BM configuration seems to break up the channel a bit earlier and has more harmonic content all the way around than the Skyline, especially the high plate Skyline. Just my observation having tried many combinations of plate and tone stack values.

I would think most of the harmonic content you are hearing is due to the different Phase inverters 9K tail and 470 ohn cathode not as much headroom there... Having a larger tail resistance (like 124# 22k) limits the maximum output voltage swing, which is of particular concern for high-power amps. For this reason a smaller tail is often required, which causes the inverted phase to have substantially more amplification(see below) than the non-inverted phase. The usual correction is to reduce the size of the inverting plate resistor. The 9K tail causes a bit more of an in balance when it hits the rails...Asymetrical clipping.... To my ears I hear thicker tone but more grit associated with a clipping PI none the less more distortion.. The BM PI uses less NFB around the power amp, which also opens the amp ." any one of these by them selves not a big difference put them together more harmonic content... Not disagreeing with you just coming from a different angle..

Gain here is not much of a factor..Just the inbalance!!

Fender Style 100k pl 22kt 820 =Inverted output -26.9155
In Phase output 25.465

Blues Master/ Marshall 100k pl 10Kt 470=inverted output -27.720
In phase 24.660


Tony VVT

Geez, I love this place! Where else are you going to get intelligent, well-informed discussion like this? I swear, I've learned more here than in 3 years of grad school...not that I was studying amps in grad school.

Structo, interesting. i have a low-plate 50W D'Lite, and the clean channel won't break up until I pretty much crank it. By that time, the clean volume overwhelms the OD volume.

[talbany]

Geez, I love this place! Where else are you going to get intelligent, well-informed discussion like this?

Careful now.... We don't like to use the I word around here much!!..


T

[Tonegeek]

The BM configuration seems to break up the channel a bit earlier and has more harmonic content all the way around than the Skyline, especially the high plate Skyline. Just my observation having tried many combinations of plate and tone stack values.

I would think most of the harmonic content you are hearing is due to the different Phase inverters 9K tail and 470 ohn cathode not as much headroom there... Having a larger tail resistance (like 124# 22k) limits the maximum output voltage swing, which is of particular concern for high-power amps. For this reason a smaller tail is often required, which causes the inverted phase to have substantially more amplification(see below) than the non-inverted phase. The usual correction is to reduce the size of the inverting plate resistor. The 9K tail causes a bit more of an in balance when it hits the rails...Asymetrical clipping.... To my ears I hear thicker tone but more grit associated with a clipping PI none the less more distortion.. The BM PI uses less NFB around the power amp, which also opens the amp ." any one of these by them selves not a big difference put them together more harmonic content... Not disagreeing with you just coming from a different angle..

Gain here is not much of a factor..Just the inbalance!!

Fender Style 12ax7 100k pl 22kt 820 =Inverted output -26.9155
In Phase output 25.465

Blues Master/ Marshall 12ax7 100k pl 10Kt 470=inverted output -27.720
In phase 24.660


Tony VVT

I agree that at a high volume the Marshall style PI does seem to break up more than the Fender version. Not sure I agree it works the same way at low volume. If I understand this correctly, you are saying that even at a low volume the PI makes an audible difference in harmonic content? I have never put a scope on it but I would not think the PI would clip unless it was hit pretty hard.

The PI is one area that still holds mysteries for me and I am very interested if at low volume it makes a difference in tone.

I think my comments about the BM clean stage still stand though. I have done experiments where I compared the Skyline, BM and Fender Bassman tone stacks while keeping all other variables including the PI, the same. In my case I started with a Skyline, then built the BM stack into the amp. For the Bassman test I sent the output of the Bassman stack to the input of the PI in my test rig. BTW the PI was a BM for all 3 tests. So the Bassman part of it was not quite as controlled as the other 2 because it was driven by the power supply in the Bassman, but still the Skyline had the cleanest, more sterile sound to my ears. The Bassman sounded the best with really nice harmonic content, but the BM was a very close second. One more thing, i thought maybe it was my old RCA tubes in the Bassman that made it sound so good, so I swapped them with my newer EH. There was almost no difference. Still sounded great. I attribute most of the sound of the Bassman to the gain, and bias settings of the circuit and maybe some to the old resistors and caps, and also maybe to the actual cap values which were .047, .1 and 250p.